Hyaluronic acid is found in a rage of topically applied skin care products. The ability to hold more than 1000 times its weight in water makes it an excellent addition to moisturizers for its humectant action (ability to draw water into the skin). Studies have also shown that hyaluronic acid can increase the presence of retinoic acid (which helps to increase skin hydration) as well as increase collagen synthesis. Hyaluronic acid degrades upon exposure to UV rays, which could be problematic if applied topically.